Abstract
Depression and coronary heart disease (CHD) are highly comorbid conditions. Brain-derived neurotrophic factor (BDNF) plays an important role in cardiovascular processes. Depressed patients typically show decreased BDNF concentrations. We analysed the relationship between BDNF and depression in a sample of patients with CHD and additionally distinguished between cognitive-affective and somatic depression symptoms. We also investigated whether BDNF was associated with somatic comorbidity burden, acute coronary syndrome (ACS) or congestive heart failure (CHF). The following variables were assessed for 225 hospitalised patients with CHD: BDNF concentrations, depression [Patient Health Questionnaire-9 (PHQ-9)], somatic comorbidity (Charlson Comorbidity Index), CHF, ACS, platelet count, smoking status and antidepressant treatment. Regression models revealed that BDNF was not associated with severity of depression. Although depressed patients (PHQ-9 score >7) had significantly lower BDNF concentrations compared to non-depressed patients (p = 0.04), this was not statistically significant after controlling for confounders (p = 0.15). Cognitive-affective symptoms and somatic comorbidity burden each closely missed a statistically significant association with BDNF concentrations (p = 0.08, p = 0.06, respectively). BDNF was reduced in patients with CHF (p = 0.02). There was no covariate-adjusted, significant association between BDNF and ACS. Serum BDNF concentrations are associated with cardiovascular dysfunction. Somatic comorbidities should be considered when investigating the relationship between depression and BDNF.
Highlights
Coronary heart disease (CHD) and depression are leading contributors to the global burden of disease (GBD 2017 Disease and Injury Incidence and Prevalence Collaborators, 2018; Rehm & Shield, 2019)
The present study showed that the somatic depressive symptoms in the Patient Health Questionnaire-9 (PHQ-9) depression scale did not show an association with brain-derived neurotrophic factor (BDNF), once the influence of somatic confounding variables was taken into account, which can be explained by the large overlap of somatic depressive symptoms and coronary heart disease (CHD) symptoms
To further improve the investigation of causalities and the specification of important confounders, the use of directed acyclic graphs (DAGs) and DAG-specific reviews for a certain field of research (e.g. Lewis & Kuerbis, 2016; Williams et al, 2018) appear recommendable in future research. This data show that severe cardiac disease is associated with lower BDNF concentrations, independent of potential confounders and depressive symptoms
Summary
Coronary heart disease (CHD) and depression are leading contributors to the global burden of disease (GBD 2017 Disease and Injury Incidence and Prevalence Collaborators, 2018; Rehm & Shield, 2019). One biological marker associated with depression and CHD is brain-derived neurotrophic factor (BDNF). BDNF plays an important role in learning and memory function (Allen & Dawbarn, 2006) and it has repeatedly been linked to depression (Brunoni et al, 2008; Bocchio-Chiavetto et al, 2010; Zhang et al, 2011; Molendijk et al, 2014). Current research assumes that synaptic and neuroplasticity have an important role of in the development and treatment of depression (Brunoni et al, 2008) via a stress-induced reduction in expression of BDNF in the limbic regions that control mood (Duman & Monteggia, 2006)
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